Methods for the preparation of (S)-2-methoxy-3-{4-[2-(5-methyl-2-phenyl-oxazol-4-yl)-ethoxy]-benzo[b]thiophen-7-yl}-propionic acid have been described in WO 02/092084. However, these methods include a large number of individual and costly process steps and exhibit a low yield. These methods known in the art are consequently unsuitable for the commercial large scale production of (S)-2-methoxy-3-{4-[2-(5-methyl-2-phenyl-oxazol-4-yl)-ethoxy]-benzo[b]thiophen-7-yl}-propionic acid.
It has surprisingly been found that using the process according to the present invention (S)-2-methoxy-3-{4-[2-(5-methyl-2-phenyl-oxazol-4-yl)-ethoxy]-benzo[b]thiophen-7-yl}-propionic acid can be prepared much more economically, with less process steps under moderate conditions with an outstanding yield. Further, crude intermediate products can mostly be used in subsequent reaction steps without the need of any additional purification steps.